Halbach Arrays | Magnet Assemblies For Tech Applications

For High-Tech Applications, Permanent Magnet Assemblies Are Used

When permanent magnets are used to generate a strong magnetic field, the array is structured with a spatially rotating magnetic field vector. This has the effect of concentrating and augmenting the magnetic field on one side of the array while canceling it out on the other side of the array. By using Halbach Arrays, it is possible to generate very high and homogeneous flux densities without the need for additional power or cooling, as would be required by an electromagnet.

In addition to multi-segmented Halbach arrays, circular and linear (planar) Halbach magnetic assemblies, we also specialize in the technical design, engineering, and manufacturing of Halbach-type magnetic assemblies, which provide multiple pole configurations with high field concentrations and uniformity.

Halbach Cylinder - Halbach Arrays in a Circular Form

One kind of Halbach array that rotates in order to concentrate the field is the Halbach cylinder, which is made up of many trapezoidal or arc-shaped magnet segments with magnetic orientation vectors that revolve in order to focus the field. They are commonly constructed in a variety of magnet configurations, including quadrupole, hexapole, sextupole, octupole, and others. As a rule of thumb, the greater the number of discrete magnets and the corresponding number of magnetic vector angles in a Halbach assembly, the more uniform the field distribution over the inner diameter of the assembly.

Three designs (A) (B) (C) producing uniform magnetic fields within their central air gap from Halbach Cylinder in Wikipedia

Halbach Cylinder - Halbach Arrays in a Linear Form

It is made up of discrete rectangular permanent magnets set on a ferromagnetic backplate with various magnetic orientations, which help to concentrate the magnetic field on one side of the array, providing a uniform and strong semi-sinusoidal magnetic field. As an alternative, linear (planar) arrays may be utilized in conjunction with a yoke arrangement to generate a highly strong sinusoidal field in the gap.

We manufacture a variety of linear (planar) Halbach arrays, which are utilized in particle accelerators, free-electron lasers, highly strong linear motors, and other applications in the industrial, life science, research and development, and medical fields, among other things.

Orientation of strong and weak side in a linear Halbach array (weak side up) from Halbach Array on Wikipedia

Halbach Array Applications

In the case of one-sided flow distributions, there are two distinct advantages:

On the side where the flux is contained, the field is twice as big as on the other (in the idealized case).
In the perfect instance, there is no stray field created on the other side of the spectrum. This aids in the containment of magnetic fields, which is often a concern in the construction of magnetic structures.
A surprising number of applications exist for one-sided flux distributions, from the refrigerator magnet to industrial applications such as brushless DC motors[7], voice coils[8,] magnetic drug targeting[9], and high-tech applications such as wiggler magnets used in particle accelerators and free-electron lasers.

Additionally, this device is a critical component of the Inductrack Maglev train[9] and the Inductrack rocket-launch system[10], in which the Halbach array repels loops of wire that comprise the track once the train has been driven to a speed that is capable of lifting them off the ground.

A refrigerator magnet's flux distribution is shown.

A refrigerator magnet is the most straightforward example of a one-sided flux magnet. The powdered ferrite is frequently mixed with a binder such as plastic or rubber to form these compounds. An alternating magnetic field is applied to the extruded magnet, which causes the ferrite particles in the magnetic compound to become magnetized, resulting in a one-sided flux distribution. As a magnet is put on a permeable surface, this dispersion enhances the holding force of the magnet when compared to the holding force produced by, for example, a uniform magnetization of the magnetic compound.

Cylinder Halbach Array Applications

They are found in a variety of electronic equipment, including brushless alternating current motors, magnetic couplings, and high-field cylinders. Multipole field configurations are used by brushless motors as well as coupling devices, as follows:

Rotary designs such as the one shown above (k = 4 for a 6-pole rotor) are common for brushless motors because they keep all of the flux contained inside the bore. The alternating current coils are similarly contained within the bore. Traditional motor designs are inefficient, whereas self-shielding motor designs create greater torque than their conventional counterparts.
Magnetic-coupling devices transfer torque via magnetically transparent barriers (that is, barriers that are either non-magnetic or magnetic but are not influenced by an applied magnetic field), such as those that exist between sealed containers or pressurized vessels, for example. In order to create a torque, the ideal torque couplings are composed of two coaxially nested cylinders with opposing +k and k flux magnetization patterns, since this configuration is the only system for infinitely long cylinders that produces a torque in the first place. [14] It is possible to have an identical match between the internal flux of the outer cylinder and its own outside flux while operating in the lowest-energy condition. Rotating one cylinder in relation to the other from this condition results in the production of a restoring torque